With the spread of E-business and the Internet, security and creditability problems become increasingly important. To solve these problems and protect secrecy in hardware and software, generally a symmetric key or asymmetric key is used in a Public-Key Infrastructure (PKI). Since the software and hard disk that protects the symmetric key or private key are vulnerable to attack, more and more applications keep such keys in integrated circuit chips, such as a Smartcard, a Trusted Platform Module (TPM), and a Field Programmable Gate Array (FPGA) that protects the Triple Data Encryption Standard (DES) keys. However, most of the approaches are either not secure enough for the hackers who hold professional tools, or too expensive or inconvenient to use.
The following are some traditional methods for protecting encryption keys in integrated circuits and their drawbacks:
Method 1
Store the keys in Application Specific Integrated Circuit (ASIC) chip or embedded read-only memory (ROM). It can be cracked though reverse engineering. Hackers/Crackers take photos of the chip after etching each successive layer and thus can easily read the information.
Method 2
Keep the keys in embedded flash memory. To crack such a chip is more difficult than Method 1, however, it is possible. One approach is to measure the potential of the floating gate electrically. Another approach is to put the powered chip into a vacuum container and measure its radiation with an electron microscope.
Method 3
Protect the keys with QuickLogic's patent ViaLink technology (see EP00416903A2). The ViaLink technology can hide the key in millions of antifuses, so it is difficult for crackers to locate it. Industry experts regard antifuse as the most secure of all programmable logic solutions. However, this technology is mainly used in FPGA and the associated device is expensive.
Method 4
Keep the keys in random access memory (RAM) and charge the RAM with an external battery. With the assistance of an effectively designed sensor, this technology can be regard as secure, but the additional battery constrains its popularization.
Furthermore, for most of the traditional methods, since the memory block is separate from other blocks and the information must be passed along a bus between the blocks, crackers can put a probe on the bus of a powered chip and read the secret.
In addition, traditional memories keep information with digital state, either “0” or “1”, so the physical property of the “0” unit is distinct from that of the “1” unit, and thus it is possible for crackers to find the approach to crack it at present or in the future.